In my Felltower game I hand out XP for treasure, which is unlike GURPS in general but which came as an option in Dungeon Fantasy 3.
I was thinking about that system and the system I grew up with in games like D&D. Not that we played it right (we often ignored the levels-per-trip thing) but sometimes we did.
A Treasure Floor, Not A Value Ceiling
In my system, I chose to put in a floor - you must find and take home at least $X per person to earn maximum XP for the session. Miss that by even a hair, and you get a penalty. Miss it by a lot, and you suffer the same penalty. It's pass/fail. We've scaled the X along with the improved power of the PCs, so you can't maximize XP by bottom-feeding. The awards are at the end of the day's gaming, too, regardless of how much in-game time passes.
The old D&D systems and D&D-based systems I'm familiar with have a ceiling. You can't earn more than one level in a single adventure. So you are restricted in maximum benefit from treasure & exploits to 1 xp less than needed to go up 2 levels. If you're got a 0 xp level 1 fighter and he scores a colossal 5000 xp payday (from all sources combined), he earns 4,000 xp - 1 xp shy of level 3, and promotes to level 2. Sure, the extra money is useful, but he's capped.
This can result in subtly different play, in my experience. With a ceiling, your goal is to hit that ceiling if at all possible . . . and not much higher. You want to earn as much as you can benefit from, at least in theory. There is such a thing as too much treasure for right now. XP can get, basically, wasted (especially with low-level guys earning a share from a treasure-filled high-level trip.)
With a floor, you want to earn at least enough to get the maximum benefit, but once you do, you're really going to benefit more from cherry picking what gets you the most value for the trouble. You don't really get short little trips just trying to get past the floor, either, because it's per session, not just per trip. Even so, since XP is earned individually, all you need to do is ensure everyone hits the Treasure Floor to ensure everyone gets the maximum XP, too.
Also I find it's much easier to eyeball a floor - going into the trip you know you need to exceed X value in loot - than a ceiling. You can grab enough and say, yes, this is profitable. It's like shopping with "with an additional purchase of $25" versus "I can only spend $50" - much easier to figure out you're over and then move on.
Is That New Loot?
Another twist that makes this work is the need to discover new treasure, not just take home X amount of loot, means you can't just stash some money for later and come back or keep hitting the same places again and again until you take all the value out. Well, you can, but you're wasting valuable game time that can earn you XP.
So that's part of the subtle difference in how I reward XP now versus how I did it back when I played D&D. It ends up with some equally subtle differences in how people think about hauling back treasure. My players still haul back just about everything, though.